In the manufacture of powdery or granular detergent compositions, it is common practice to prepare a relatively high solids aqueous crutcher slurry containing a surfactant ingredient, a builder ingredient and water. The crutcher slurry is then spray dried to form the desired powdery or granular detergent product.
When preparing a powdered or granular detergent in the foregoing fashion, there is a significant economic incentive to minimize the amount of water present in, and to maximize the dry solids content of, the crutcher slurry, thereby reducing the amount of energy required in drying the slurry to form the desired granular or powdered detergent product. Naturally, however, there are also practical upper limits within actual granular or powdered detergent manufacturing operations upon the maximum solids content which can be achieved while still providing a pumpable/sprayable slurry as well as upon the combinations of ingredients, suitable for preparing stable, homogeneous high solids aqueous crutcher slurries or suspensions.
While attempts at increasing the solids content of aqueous crutcher slurries used to form granular and powdered detergent products have shown to be successful, their use in today's institutional and industrial spray washing machines is not pragmatic for various reasons. In the past, conventional institutional and industrial spray washing machines employed liquid or powdered detergents which were generally added to the wash tank by means of an automatic dispenser system. All forms of such detergents, whether liquid or solid, have stability problems and other problems associated with their manufacture, dispensing or use. Moreover, in the early days of the development of solid detergents, when these detergent products were relatively low in performance compared to the products of today, the problems were less severe. However, the advent of high performance products stimulated in part by increased aesthetic and sanitary standards and a demand for shorter wash times has generally been characterized by the development of more complex detergent compositions which are more hazardous to the user, less stable, and more difficult to dissolve in a satisfactory uniform manner.
For example, higher performance solid detergents generally means higher alkalinity, i.e., greater concentrations of sodium hydroxide, higher to the point of posing safety hazards to the user. Historically, detergents used for warewashing have been relatively low in alkalinity. The extensive use of aluminum trays and utensils, the presence of soft metals in wash pump impellers and other factors generally prevented the use of high alkalinity detergents. Today, however, there has been a trend toward the use of high alkalinity, higher performance products. This trend has been partially the result of the increased usage of stainless steel and corrosion resistant plastics in the production of utensils. In addition, the aforementioned increased standards and shorter wash times required by the increased volume of business in eating establishments have created a demand for these higher performance products.
In an effort to minimize the contact between the user and the detergent composition, solid cast detergents have been introduced. These detergents originate in aqueous form and are subsequently cast (hardened) into a solid homogenous block of detergent. These detergent blocks are then inserted into warewashing machines and dispensed by spraying water over the block, thereby releasing a predetermined amount of the detergent for use in cleaning.
While cast detergent products by and large provide adequate cleaning and wash times, there still exists a need for more concentrated cast detergent products which provide greater cleansing power in even shorter time periods. One way to meet these demands is by increasing the solids content of the cast detergent product, thereby providing for a more concentrated product having increased levels of cleaning ingredients.
Moreover, by increasing the solids content of the aqueous detergent slurries used to make the solid cast product, less time and energy are required for the product to cast (harden). Hence, by increasing solids content, a more concentrated and cost-efficient product is formed.
The mere addition of more solid detergent ingredients to an aqueous slurry, however, is not the solution since an increase in solid ingredients alone such as anionic surfactants causes the aqueous slurry to become too viscous to handle, thereby precluding the formation of an acceptable homogeneous solid cast detergent product.
It is therefore an object of the present invention to provide a process for producing solid cast detergent products having high solids content levels by reducing the initial viscosity of the aqueous slurry prior to casting, thereby controlling both the set-up time of the slurry and the final hardness of the solid cast detergent product.